The field of invention is electrical circuit packages, and particularly, electrical circuit packages which have conductive material and components on a flexible support member with the support member being integrally molded with a plastic substrate material.
In U.S. Pat. No. 2,972,003, there is disclosed a circuit assembly wherein a circuit pattern is die stamped from a metal foil and adhesively secured to a fibrous base. The circuit pattern is subsequently molded into the base. In one embodiment there are three fibrous bases sandwiched together.
There is known in the electronic art to provide printed circuit boards wherein electronic components are mounted on insulating substrates. Such methods of making printed circuits are described in U.S. Pat. Nos. 2,692,190 and 3,181,986. In U.S. Pat. No. 2,692,190, a temporary base sheet is employed on which is placed a conductive material utilizing a photo-sensitive coating process as well as an etching step. A copper sheet is used as a temporary base which is etched away leaving the conductive material in a base of insulating material. In U.S. Pat. No. 3,181,986 a metal film with the circuit is stripped from a base of insulating material leaving the circuit material in the base.
Another well known product of this general type employs fiberglass laminated substrates. This involves the interconnection of the mounted components by conductive traces such as copper which are etched onto the board surface. This is a time consuming and labor intensive task in that a typical board would require plating, etching, drilling and cutting. Once a standard board is complete, retainer clips, sockets and standoffs must be added. The problems which are inherent to the fiberglass laminate substrate include warpage, poor dimensional stability, low glass transition, temperature and limited electrical properties. Printed circuit board production also can create physical and chemical wastes which must be recovered or disposed.
Modern, so-called "engineering plastics", are increasingly being used as parts, sub-assemblies or structural members in all kinds of manufactured goods; such as motor cars, aircraft, "white" goods, and telecommunications equipment. There is often a requirement to incorporate an electrical circuit on such parts and, hitherto, this has been achieved by printing, bonding or otherwise applying the circuit onto the surface of such parts to effectively produce a "printed" circuit on an external surface of a three-dimensional object. The printed circuit may include integrally formed resistors, capacitors and inductors and may also have other devices added to the circuit.
It is also known to utilize a decal or temporary support base for a printed circuit which is transferred to the permanent substrate. An example of this type of process is indicated in U.S. Pat. No. 4,415,607 as well as U.S. Pat. Nos. 4,050,976; 4,301,580 and 4,407,685. Basically, the process described in U.S. Pat. No. 4,415,607 is referred to as the transfer decal method and involves the printing of a circuit onto a film such as Mylar. The decal is inserted into a mold die with the circuitry inverted. After injection molding, the decal is removed, exposing the circuitry which has been transferred into the substrate material. The final product offers embedded circuit traces which are flush with the substrate surface.
There is a need, however, for a molded circuit board which would involve fewer processing steps and result in an overall cost saving. It would provide for holes, standoffs and numerous other physical features which could be molded into the circuit board eliminating the need for drilling, cutting and additional hardware placement. As a decal is involved it is flexible, and can conform to a three dimensional surface created during the molding process. This gives a true three-dimensional circuit capability. This offers the advantage of uniform placing of components and flexible backing which assists in handling and high speed production. Such a product is provided in the product of this invention.